The invention relates to a rotary ceramic tile glazing and decorating machine. The prior art teaches such machines wherein the decoration of the tiles is effected by means of a transfer system, widely used in printing, where the pattern is engraved on a chalcographic drum, which is first supplied with glaze and when rotating contacts an underlying and also-rotating intermediate transfer roller. The underlying roller is in direct contact with the tile and transfers thereto the pattern originating from the engraved drum. A horizontal conveyor advances the tiles, which are then pushed under the intermediate transfer roller, which latter is covered in rubber so as to exhibit a slight elastic deformability in order to adjust to small breadth differences between the various tiles passing thereunder. A support roller, positioned below the intermediate roller, compresses the tile (with a predetermined pressure) against the intermediate roller during the printing phase. An apparatus of this type is described in European Publication no. 278650.
Also disclosed in the prior art is the use of silk screens for decorating tiles, wherein the transfer of the glaze on to the tiles is performed through the cylindrical surface of the screen, which rolls on the tile. The glaze inside the screen is pushed outwards by spatula devices.
All the illustrated embodiments, both indirect (with the presence of an intermediate transfer roller) and direct (using a rotary silk screen) present numerous drawbacks which render them useful only in a small number of applications. In particular, they are used almost exclusively in decorations reproducing, for example, veined stone or marble effects and the like.
Finally, the prior art solutions do not afford constant results, as it is impossible to obtain multicolored patterns of an acceptable quality, that is of a quality which can be obtained using traditional flat and single-color dedicated silk screens.
A further common drawback in the prior art applications, especially those wherein the decoration is performed by indirect transfer of the image, is that it is difficult to achieve a perfect cleaning operation on the transfer roller, and therefore guarantee a perfect reproduction of the pattern on the tile.
With regard in particular to rotary silk screen apparatus, further drawbacks are inherent in relation to the structure of the screen itself, which includes internal ribbing.